1. Field of the Invention
This invention relates generally to inflatable type modular occupant restraint systems for passenger vehicles, or, as they are more commonly known, air bag restraint systems. More particular, this invention relates to an improved rigid filter assembly for use in a pyrotechnic air bag inflator and a method for manufacturing the filter assembly. The filter functions to cool the hot gases before they reach the air bag and serves to trap particulates and residues generated during ignition so that they do not enter the air bag and contaminate the vehicle.
2. Description of the Related Art
The state of the art today for manufacture of passenger inflator filters consists of metallic screen or mesh materials which are constructed by being wrapped around a rigid perforated cylinder or tube which provides strength and support for the filter. A combustion screen, which provides cooling and helps retain the generant slag inside the filter, is inserted into the interior of the perforated support tube and welded thereto. The use of a perforated support tube adds little value to the filter assembly and/or the performance of the filter in its deployment in air bag inflator systems. Rather, the use of the perforated support tube requires additional assembly operations in that the filter assembly must be clocked during manufacture and assembly of the inflator to provide proper alignment and this adds to the cycle time and cost required to manufacture the inflator. A filter assembly of the aforesaid type is disclosed in U.S. Pat. No. 5,109,772 and is assigned to he assignee of the present invention.
The consistent and economical manufacture of filter assemblies for passenger side inflators which efficiently cool and clean gas from the gas generant is of prime concern. The elimination of parts as well as process steps in the manufacture of such inflators has obvious advantages and benefits. Also advantages provided to the filter in reducing the cycle time for manufacturing the inflator result in obvious economic savings.